Verified

For some time it has been ordinary practice to protect and transport a key for the DES encryption with triple-DES. This signifies that the plaintext is, in effect, encrypted three times. There are, obviously a range of ways of doing this; we will explore such ways below.

A number of modes of triple-encryption have been suggested:

DES-EEE3: Three DES encryptions with three distinct keys.

DES-EDE3: Three DES operations in the series encrypt-decrypt-encrypt with three distinct keys.

DES-EEE2 and DES-EDE2: Similar to the prior formats except that the first and third operations use the similar key.